I would like to apply to USC, UCLA, UC Berkeley, etc. like the top california schools, excluding stanford. I am a biochem major but I don’t know if I should apply undecided or as a science-based major. Which one would make me more likely to be accepted?
It makes no difference. I’ve heard many admissions officers say that they really don’t pay attention to intended majors since about half of the applicants apply undecided and half of the applicant who apply with a major end up switching while they are in college. The only thing you need to be sure is that you apply to the school where your interests are (ex. if you want business, engineering, nursing etc. you usually need to apply to that school or program).
Actually, it does at many schools. The answer to this question is specific to each school – relying on generalizations can be a mistake.
At Berkeley, applicants to the College of Letters and Science are considered as one pool, with no distinction by intended major, and all matriculating frosh are undeclared. However, the College of Engineering and College of Chemistry have different levels of selectivity, and the College of Engineering has different levels of selectivity by major. So, for Berkeley, the answer depends on whether “biochemistry” means molecular and cell biology (in the College of Letters and Science) or chemical biology (in the College of Chemistry).
Since you are only a sophomore it is a little too early to pick.